Heat loss around windows

I've just surveyed a lovely old Welsh stone cottage. It was interesting in being warm and dry - and had just had UPVC windows fitted all round. Now I know I don't like these, but in this case, they are doing a good job - the windows are warm, and are not losing heat. What is very obvious though is that heat is being lost AROUND the windows, through the reveals. This is very typical of such solid walled buildings. Most heat actually does get lost around the windows, not through them. You can see here that where the wall is very thin - heat is able to leak around the frames. This is the cause of the very common mould and mildew patches around windows - often we see little areas of mould in the corners or on the reveals at the bottom.

How do we stop this?

The best way to prevent heat loss in window reveals is to insulate them. In an old solid walled building, it's almost certain that modern gypsum or cement plaster will now be present - so we first chop everything off - take it back to clean stone or brick. Then we re-plaster using a hemp lime mix - hemp is a really good insulator, and added to the lime, gives it good qualities. Thicken it as much as possible into the window frame, and you will find heat loss is then minimised.

This is actually a major issue in old houses - heat is not lost through the main walls - but window openings are a big contributor to heat loss. The devil is in the detail - and in this case, going back to old technology like hemp lime, is a really good way to keep your solid walled 'old' house cosy and warm.

Dark purple indicates cold areas around the window where heat is being lost.

UPVC window in solid walled limestone cottage. Heat lost AROUND the window through reveals, not the window itself.

It's Condensation Season!

The Haynes Manual for Period Property

Ian Rock has written another of his great books. This one is even better - We've helped Ian with this one and there's loads of photos of our guys doing timber frame work. A great book, with lots of practical information you need if you have an old home. Treat yourself and buy this - you won't regret it!

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About Us

The Heritage House brand was Petes brainchild. He lives in a beautiful old farmhouse in Shropshire with mad horse - Lucy. He's worked all over the world on old buildings, and with a strong background in geochemistry is passionate about ensuring the 'Rising Damp' myth is firmly buried. His Partner, Richard handles work in London. Pete has an all consuming project to re-open a Victorian lead mine in the Northern Pennines - digging out and exploring miles of abandoned tunnels in the search for crystal lined cavities... The shaft they've dug is currently 250 feet deep! Just before Christmas, Pete broke into the first of the crystal filled workings and is cleaning and preparing beautiful crystal specimens of fluorite.

The website is owned by Campylite Investments Ltd (campylite). Pete and the crew are consultants to campylite and sister company, Heritage Consulting Ltd.

Disclaimer

Note! The opinions expressed on this website are often Pete's. They are frequently strong, unambiguous, and based on extensive experience of what goes on out there. Pete does not like to see the buying public being conned, defrauded, duped, sold a lemon, given bad or misleading advice, or crap surveys using equipment that is unsuited for the job. If you don't like what is written here - don't threaten us - clean your act up.